Sulphite wood pulp and method of making the same



Aug. 19, 1930. w. E. B. BAKER n 1,773,419

SULPHITE WOOD PULP AND METHOD OF MAKING THE SAME Filed June 3, 1926Patented Aug. 1e, 1930 y d 1,7 73,419v

UNITED STATES PATENT OFFICE WEBSTER E. BYRON BAKER, OF BROOKLYN, NEWYORK SULPIEIITE WOOD PULP AND METHOD OF MAKING THE SAIE Applicationfiled June '3, 1926. Serial No. 118,408.

The principalobjects of the present invendigesters. As shown these meanscomprise a. tion are to increase the yield and improve the closedreceptacle 8 in a closed valved pipe quality and strength of unbleachedsulphite circuit Q, which includes a pump 10 and pulp suitable formaking wrapping and bag which communicates by valved branches 11 Upaper; to improvethe fibers; to shorten they with the digesters, andthere is also a valved 55 sulpliite cooking period; and to provide anconnectionI 12 between each of the digesters. economical and effectiveprocess for obtain'- The method or improvement of the inveninG theforegoing objects. tion may be described in connection with the Itatedgenerally, the invention consists in apparatus above referred to asfollows:

10 treating wood chips with alkali solutions In the descriptionreference will be made 30y adapted to render'their alpha li nininsoluble at first to one digester, for. example 3. The in bisulphitecooking liquor be ore digesting digester is properly supplied with woodchips the chips in bisulphite cooking liquor. and the chips aresubjected to weak alkali The invention also comprises rendering solutionand steam by wa ofthe connections 15 the alpha lignin `insoluble in thesubsequent 4 and 11. The result o this is that alpha 55 step of cookingwith bisulphite acid solution lignin is rendered insoluble Ain thecooking by treating thewood chips with an alkali acid employed at alater stageof the process solution containing or consisting of freeact.- and in the usual way. An example of weak ing ammonia which,augmenting the vapor alkali solutions are solutions of caustic soda,

pressure at the tempera-ture employed in the barium hydrate and thelike. A' descriptive 7 digester, forces the alkali solution into the butnot limiting example of temperature is pores of the chips, l 90'to 100C. more or less and as a descriptive,

The invention also comprises sulphite pulp but not limiting, example ofan alkali solucharacterized by abnormally high lignin contion adapted torender alpha lignininsoluble tent and by the strength and flexibility ofits in the subsequent cooking step, reference may 75 bers, be made toone differing only by a few hun- The invention also comprises theimiplilgovedredths specific gravity departure from waments to bepresently described and ally ter, more or less. Stronger solutions ofalkali claimed, and in the following description effect economy in time`at the expense of 30. reference will be made to the accompanyingeconomies in chemical consumption. The 8u drawing forming part hereofand in which duration or length of the treatment varies, the Singlefigure, more or less diagrammatibut descriptively reference may be madeto cally,` illustrates one form 0f apparatus 1n one or two hours. Thedescribed treatment connection with which the invention may be of thewood chips in the digesterA may well 8, practiced. i be carried on inthe presence 4of ammonia. thIIl the dlnllg 1, dalll aiglgesri which,creating relatively high vapor prese genera ype 11S g P sure at thetemperature employed, forces the Wd Rulll) lzomlwood chllps lydookngphllsolution into they pores of the wood. The Wlth blsu p lte' lquor' aclges er 1S ammonia can be supplied along with the al- 9o ted withsteam'connections 4 leading to the` top and bottom and provided withvalves kali solution in the manner described or 1t and also. with valvedVblow olf or dischar may. be. lnlected /mto .the digester Upollconnections 5, and also with valved connefl; comllletlon of thefiescnbed Stel) the alkall tions 6 for bis'ulphite cooking acid, andalso Solutlon, may be Wflflhdlawll by Way 0f the 5 with valved reliefconnections 7 for air, sul- Connectlon 11g OLT 1t may be Passed by Way95 phurous acid gas or vapor, SO2, and bisulofthe connection 12 'intothe digester 2 filled pliite cooking acid. There isv ynothing new withwood chipsgaiid used in the treatment involved in the a pa: atus abovedescribed. of the chips in the digester '2, and in the There are meansor introducing and withlattercase an economy is effected in that the 5drawing weak alkali solutions to and from the heat of the alkalisolution is imparted tothe o chips in the digester 2 and is not wastedor 10st. 4

The next step is the well known step of cooking the chips for example inany of the 5' digesters shown, or in digester with bisulphite liquor orcooking acid which step is too well understood tolrequire detaildescription. The pulp is finally discharged as at 5 and it of coursecontains the alpha lignin so that the-yield is increased and the fibersare improved by having been subjected to the swelling effect of hydroxylions in the first treatment and to the-shrinking effect of acid in thesecond treatment or step. In respect to the step of cooking in acidliquor there are advantages due to the primary treatment of the woodchips in the digester with an alkali solution as described,

and lamong these' advantages reference may i anbe made to the fact thatthe discharge of the weak alkali solution from the digester leaves apartial vacuum which'promotes the penetration of the chips by thecooking acid. Resin saponiication and elimination from 5 the wood by theweak alkali solution treatment previous to cooking facilitatespenetration of the cooking acid into the porespf the chips. The resultvof these factors is that the sulphite cooking periods are made shorter,

jjo thus effecting Aan economy additional to the economyeected byincreased 'eld while at thevsame time the quality of t e wood pulp isimproved in regard to strength, flexibility and otherwise for. uses andpurposesof which v u ba and wra ping paper are examples. twill be oviousl to thoseskilledinthe art that modifications may bemade in'detailsof procedure and in thel ifchoice of the alkali solution or ofthe ori'nal raw material with- 40 out departin from t e spirit of the inventionwhich is not limited in'those respects or otherwise than as'the priorartand the appended claims may requlre. I claim:

1. In the' manufacture of sulphite wood pulp the improvement whichconsists in rendering the alpha lignin insoluble in the subsequent stepof cookingivvith bisulphite acidy liquor by primarily treating woodchips in a digester with an alkali` solution including free actingammonia which creating relative- 1y high vapor pressure at thetemperature employed forcesthe alkali'solution into the pores of thewood. l v

2. In he manufacture' of sulphite wood pulp'the improvement `whichconsists in establishinga plurality .digesters containing wood chips,primarilyl treating the wood 50 chips -in one digesterl alkali solutioni fl introducing isulphite acid cooking adapted to render alpha lignininsoluble,

transferring the solution while hot from the first dlgester to aSecond-.digester and there treatlng chi s with the hot solutio andl1liquor ter and thereby creating a partial vacuum,

and introducing bisulphite cooking liquor and cooking the chips.

4. In the manufacture of 'sulphite wood pulp the improvement whichconsists in treatlng wood chips in a digester with alkali solutionincludin free acting ammonia, removing the solutlon and thereby creatinga partial vacuum, and introducing bisulphlte cooking liquor into thepartial vacuum and cooking the chips.

5. Sulphite pulp characterized by abnormally high alpha lignin content.

6. Sulphite pulp characterized by abnormally hlgh alpha lignin contentand by strength and flexibility of its fibers exceedin that where thebeta lignin is present.

Sulphite wood pul contalning alphal lignin in a form insolub e inbisulphite acid cooking liquor.

8. Sulphite wood ul of low resin content and containing alpha lignin ina form insoluble in bisulphite acid cooking liquor.

9. In the manufacturepof sulphite wood pulpthe improvement whichconsists in initially-preparing the wood chips for cooking by treatinthem in a digester with alkali solutionan limiting the action of thealkali by'-flow temperature and low concentration `such that none of thelignin is cooked and the alpha lignin is rendered insoluble in thesubsequent step of cooking withbisulphite liquor, and then pulping theso treated chips by cooking them with bisulphite liquor.

10. In the manufacture of-sulphite wood pulp the improvement whichconsists in primarily treating the wood chips in a digester with analkall solution differing only by a few hundredths specific avitydeparture from water to render the' pha lignin insoluble in thesubsequent step of cooking Vwith bisulphite li uor, and then pulpin theso ireated chips y cooking them with bisulphite quor. v 11. A processfor manufacturing pulp in twostages of which the Erst is a treatment ofthe wood chips with alkali solution differing only by a few hundredthsspecific avity departure from water, and of whic 'the secon comprisesanacid treatment of the chips resultm in the production of, ulp.W'EBS'I'ER E. BYRON B uns`

